High melting point synthetic base grease containing an alkali metal salt of a dicarboxylic acid



United States atent HIGH MELTIN G POINT SYNTHETIC BASE GREASE CONTAININGAN ALKALI METAL SALT OF A DICARBOXYLIC ACID Warren C. Pattenden,Courtright, Ontario, Lorne W. Sproule, Sarnia, Ontario, and James H.Norton, Corunna, Ontario, Canada, assignors to Esso Research andEngineering Company, a corporation of Delaware No Drawing. Filed Sept.23, 1957, Ser. No. 685,395

Claims. (Cl. 252-41) This invention relates to greases and greasethickeners and to methods for their preparation. In particular, itrelates to grease compositions comprising a major proportron of alubricating oil and a thickening amount of a thickener comprising a saltof a dicarboxylic acid and to methods for preparing the greasecompositions.

This application is a continuation-in-part of US. application Serial No.605,726, filed August 23, 1956, and now issued as US. Patent No.2,898,296.

Salts of dicarboxylic acids are known to have high melting points butare usually so indispersible in mineral oil that they have found littleuse in grease manufacture. It has now been discovered that greasethickeners having high dropping points can be prepared by the directreaction of a metal base with either a dibasic acid ester or with amixture of an aliphatic dicarboxylic acid and a monohydric aliphaticalcohol. It has also been discovered that excellent grease thickenerscan be prepared in a lubricating oil menstruum from a'mixture of analiphatic monocarboxylic acid salt and a metal salt of a dicarboxylicacid, the latter salt being obtained by saponification of the diester ofthe dicarboxylic acid. The latter thickeners maybe prepared byneutralizing a mixture of an aliphatic monocarboxylic acid and asynthetic ester of a dicarboxylic acid with a metal base in either amineral oil or synthetic oil menstruum. Greases prepared with any of theabove grease thickeners are homogeneous in appearance and haveexceptionally high dropping points.

The synthetic diesters useful in this invention are those formed by thereaction of an aliphatic dicarboxylic acid and a monohydric aliphaticalcohol. These diesters have the general formula:

ROOC--(CH -COOR wherein R and R are alkyl radicals of eitherstraightchain or branched-chain aliphatic saturated monohydric alcoholscontaining about 1 to 22, advantageously 1 to carbon atoms per molecule,and x is a number from 0 to 20, advantageously 4 to 8. The diestermolecule will contain a total of about 4 to 64, advantageously 6 to 28carbon atoms. Also included are diesters prepared from Oxo alcohols,which are an isomeric mixture of highly branched-chain primary alcoholsprepared by the 0x0 process, which is well known in the art.

The aliphatic monocarboxylic acids useful in carrying out the inventionare those acids'which have about 6 to 30, advantageously 10 to 18 carbonatoms per molecule. These aliphatic monocarboxylic acids may besaturated or unsaturated, straight or branched-chain, and may be hydroxysubstituted.

The monohydric aliphatic alcohols used in the mixtures which contain analiphatic dicarboxylic acid are either 2,937,993 Patented May 24, 1960straight-chained or branched-chained aliphatic saturated monohydricalcohols containing about 1 to 22 and preferably 1 to 10 carbon atomsper molecule.

The aliphatic dicarboxylic acids used in accordance with this inventionhave the following formula:

HOOD-(CH -COOH wherein x is a number from 0 to 20, advantageously from 4to 8.

Metal bases of any of the metals commonly used in making greasethickeners may be used to neutralize the mixture of an aliphaticmonocarboxylic acid and a synthetic ester. Generally used are the alkalimetal and alkaline earth metal hydroxides or oxides. These may be usedin the form of a hydrate or in water solution.

The metal bases contemplated'for use with mixtures not containing analiphatic monocarboxylic acid are the alkali metal bases lithiumhydroxide and sodium hydroxide used in the form of a hydrate or in anaqueous solution. It was found that it was not possible to substitutecalcium hydroxide for the alkali metal bases in the process notemploying an aliphatic monocarboxylic acid.

The menstruum for preparing the thickeners may be a mineral oil, asynthetic oil, or a synthetic diester oil of the 'type used to form thethickener. When the menstruum is a synthetic diester oil, only a portionof the synthetic diester is converted into the thickener, depending uponthe amount of metal base which is used. After the grease thickener isformed by the reaction with a metal base, additional mineral oil,or-additional synthetic ester oil, or even additional amounts of anyofthe other known synthetic oils may be added to form the final greasecomposition.

,The grease cooking temperature is generally determined by the bo-ilingpoint of the alcohol which is added to the mixture or formed by thesaponification of the diester, depending on which variation of theprocess is used. The presence of too much alcohol in the final greasereduces the yield and dropping point appreciably. It is thereforedesirable to cook the grease sufficiently to remove the alcohol which'is added or which is formed during the process. Generally used aretemperatures of about 300 to 500 R, preferably 300 to 400 F. Lowertemperatures can be used if the alcohol is removed under reducedpressure. The mixture is thenheated for a period of time suflicient tocomplete the neutralization of the acids, form the thickener, and toevaporate the alcohol. This period of time will generally be about 5 to120 minutes, usually 10 to 30 minutes.

Additional lubricating oil and additives may be added to form the finalgrease product. The grease may then be homogenized through aManton-Gaulin homogenizer or a similar type of homogenizer, andpackaged.

The grease compositions of the invention consist of -a major proportion,60 to 95 wt. percent, preferably to 93 wt. percent, of a lubricating oiland a thickening amount, about 5 to 40 wt. percent, preferably 7 to 25wt. percent of the grease thickener. The grease thickener containing analiphatic monocarboxylic acid comprises about 20 to wt. percent,preferably 30 to 70 wt. percent of the aliphatic monocarboxylic acidsalt and about 80 to 20 wt. percent, preferably 70 to 30 wt. percent ofthe dicarboxylic acid salt.

The invention will be better understood by the following illustrationswhich include the preferred embodiments of the invention.

and a'V.T.C. of 0.83.

A grease was prepared by mixing 15 grams of di-(2- ethyl hexanol)sebacate with 81.7 grams of a silicone lubricating oil having aviscosity at 100 F. of 475 cst. 3.3 grams of LiOHH O were added and themixture was then heated to a temperature of about 400 F. and maintainedat this temperature for about 15 minutes. The 2-ethyl hexanol whichformed during the reaction was driven off almost as rapidly as itformed. The grease was then cooled and inspected.

EXAMPLES II TO IV Additional greases were prepared in the mannerdescribed in Example I using the ingredients as noted in Table I. Thecomposition of the greases of Examples I a through IV and theircharacteristics are likewise shown in Table I.

Table I Example Number. I II III IV 30. 33 33 L'O 6. 6 NaO'FI 10 DowCorning Fluid 710 l 81. 7 57 57 Mineral Oil 1 64. 0 Inspections:

AS'IM micropenetration, mm./

10 at 8O 74 48 400+ Dropping Point, F 500+ 680+ 580+ 1 Dow Corning Fluid710 is a silicone fluid having a viscosity at 100' F. of 475 est. and aV.T.O. of 0.83.

9 A solvent treated and dewaxed Canadian distillate having a viscosityat 100 F. of 550 S.U.S., and a V.I. of 90.

The following greases are examples of the process using an aliphaticdicarboxylic acid and a monohydric aliphatic alcohol as startingmaterials in place of the above dicsters. These greases can be preparedby slowly adding an aqueous solution of the alkali to the acid andalcohol dissolved in lubricating oil or the dicarboxylic acid can bedissolved and/ or dispersed in a suitable volatile solvent such as2-ethyl hexanol or water, and this solution then added to an aqueousalkali, alcohol, lubricating oil mixture.

EXAMPLE V A grease was prepared by mixing 20 grams of adipic acid and 36grams of 2-ethyl hexanol with 100 grams of a silicone lubricating oilhaving a viscosity at 100 F. of 100 cst. and a V.T.C. of 0.78. 11 gramsof LiOH.H O dissolved in water were added and the mixture was thenheated to a temperature of about 400 F. and maintained at thistemperature for about 15 minutes in order to complete the reaction anddrive off the water and alcohol. The grease was then cooled andinspected.

EXAMPLES VI TO VIII Additional greases were prepared in the mannerdescribed in Example V using the ingredients as noted in the followingTable II. The compositions of the greases of Examples V through VIII andtheir characteristics are shown in the following table.

4 Table II Example Number VII VIII Composition in grams:

dipie acid Sebacic acid Z-ethylhexanol- LIOH.H2O Dow Corning Fluid 550 1Mineral Oil 2 Inspections:

ASIM micropenetration mmJlU. ASTM dropping point 1 Dow Corning Fluid 550is methyl phenyl polysiloxane fluid having a flash point 01675 F. and aviscosity oi 10D est. at F.

7% mineral oil having a viscosity of 300 5.8.U. at 100 F. and a v.1.

In order to show that the salt of a dibasic acid and the soap of analiphatic carboxylic acid does not form the same type of thickener asthe saponified mixture of an aliphatic carboxylic acid and diester oralcohol-dicarboxylic acid mixtures, the following experiment was made.

EXAMPLE IX A grease was prepared by heating 10 wt. percent stearic acid,4.8 wt. percent sebacic acid, 3.6 wt. percent LiQH.H- O (suificientLiOH.H O to neutralize both acids) and mineral oil, to 300 F. Thisgrease had a dropping point of 360 F. and contained most, if not all, ofthe lithium sebacate as coarse visible particles. Attempts to disperseor redisperse the salt of the dicarboxylic acid, once it had separatedinto the grainy state, have been unsuccessful, even when the grease washeated to 500 F. Since the dropping point of lithium stearate grease isabout 370 F., it is apparent that little or no lithium sebacate has beencodispersed with the soap.

EXAMPLE X A grease of the invention was prepared by mixing 10 grams ofstearic acid and 10 grams of di-2-ethyl hexyl sebacate (equivalent to4.8 grams of sebacic acid) with 80 grams of a mineral lubricating oilhaving a viscosity at 100 F. of 300 S.U.S. and V1. of 70. 3.6 grams ofLiOHH O were added and the mixture was then heated to a temperatureof'about 400 F., and maintained at this temperature for about 15minutes. The 2-ethylhexanol which formed during the reaction was drivencit almost as rapidly as it'formed. The grease was then cooled andinspected.

EXAMPLES XI TO XV Additional greases of the invention were prepared inthe manner described in Example X using the ingredients as noted inTable HI. The compositions of the greases of Examples X through XV, andtheir characteristics, are also shown in Table HI.

EXAMPLE XVI A grease of the invention was prepared by mixing 13.7 partsby weight of stearic acid and 19.4 parts of diethyl adipate (equivalentto 14.0 parts of adipic acid) with 58.2 parts of Diol 50 at atemperature of 200 F. in a Manton-Gaulin homogenizer. The mixture wascirculated through the homogenizer and a water slurry containing 8.7parts of calcium hydroxide was added. The resultant mixture was thencirculated for 6 hours at temperature of 200 F. and a pressure of 2,000lbs. Thereafter, the grease was removed and transferred to a greasekettle where it was dehydrated at a temperature of 400 F. The greasewas, then cooled and inspected.

Table III Example Number IX X XI XII XIII XIV XV XVI Composition ingrams:

Btearic Acid 10. 10.0 10.0 10.0 10.0 10.0 10.0 13. 7

Sebaeic Acid..." 4. 8

Di-2-ethyl hexyl sebacate 10.0 10.0 10.0 10.0

Di-2-ethyl hexyl adipatel0. 0 10.0

Diethyl adipate 19 4 LiOH.HaO 3. 6 3. 6 3. 9 4. 0 4.0 4.0

a(0 s 8, 7 Mineral Oil (Viscosity at 100 F.

300 SUS; V.I. 70) 80.0 80.0 51.0 80.0 20.0

Di-2-ethyl hexyl adipate (as oil). 60. 0

Dow Corning Silicone Fluid 500 76. 0

Diol 50 58. 2 Inspections:

ASTM penetration, 77 F 320 250 220 270 AS'IM wkd. penetration, 77 F" 350265 265 310 340 300 250 273 ASTM Dropping Point, F 360 500 500 485 479500+ 640+ 450+ pp arance (0 0) (0 0) (0 (0 1 Ucon LB-1800X is awater-insoluble poiyalkylene glycol type of lubricating fluid which ispredominantly polypropylene glycol, and has a viscosity at 100 F.

of 1800 SU 1 Dow Corning Silicone Fluid 550 is a phenyl methylpolysiloxane having a flash point oi As seen from Table III, the greasesof the invention (X through XVI) had very high dropping points of fromabove 450 F. to above 540 F. and formed homogeneous products. However,the grease formed by the neutralization of the stearic acid and sebacicacid (IX) had a dropping point of only 360 F. and contained manyundispersed particles.

Various other additives may be added to the grease composition of theinvention, such as oxidation inhibitors, dyes, metal deactivators,corrosion inhibitors, deodorants, and so forth, as understood by thoseskilled in the art.

What is claimed is:

1. A process for preparing a lubricating grease composition comprising amajor proportion of a lubricating oil and about to 40 wt. percent of analkali metal salt of a dicarboxylic acid which comprises heating amixture of an alkali metal base, lubricating oil, an aliphaticdicarboxylic acid containing from 2 to 22 carbon atoms per molecule anda monohydric aliphatic alcohol having from 1 to 22 carbon atoms permolecule, said heating taking place at a temperature in the range of 300to 500 F. for a time sufficiently to form said metal salt and toevaporate said alcohol.

2. A process according to claim 1 wherein said lubricating greasecomposition comprises about 60 to 95 wt. percent of said lubricating oiland about 40 to 5 wt. percent of said thickener.

3. A process for preparing a lubricating grease composition having towt. percent of a lubricating oil and 40 to 5 wt. percent of an alkalimetal salt of a dicarboxylic acid which comprises heating to atemperature in the range of 300 to 500 F. for a time in the range of Sto minutes, a mixture of (1) an alkali metal base, (2) a lubricatingoil, and (3) a mixture of a C to C aliphatic dicarboxylic acid and a Cto C monohydric aliphatic alcohol, said heating being sufiicient to formsaid metal salt and to remove substantially all of said alcohol.

4. A process according to claim 3 wherein said alkali metal base is usedin an aqueous solution.

5. A process according to claim 3 wherein said metal base is taken fromthe group consisting of lithium hydroxide and sodium hydroxide.

References Cited in the file of this patent UNITED STATES PATENTS2,363,514 Farrington et a1. Nov. 28, 1944 2,528,373 Knowles et al. Oct.31, 1950 2,583,607 Sirianni et a1 Jan. 29, 1952 2,699,428 Lux et alJamil, 1955 2,710,838 Morway et al. June 14, 1955 2,801,220 Smith July30, 1957

1. A PROCESS FOR PREPARING A LUBRICATING GREASE COMPOSITION COMPRISING AMAJOR PROPORTION OF A LUBRICATING OIL AND ABOUT 5 TO 40 WT. PERCENT OFAN ALKALI METAL SALT OF A DICARBOXYLIC ACID WHICH COMPRISES HEATING AMIXTURE OF AN ALKALI METAL BASE, LUBRICATING OIL, AN ALIPHATICDICARBOXYLIC ACID CONTAINING FROM 2 TO 22 CARBON ATOMS PER MOLECULE ANDA MONOHYDRIC ALIPHATIC ALCOHOL HAVING FROM 1 TO 22 CARBON ATOMS PERMOLECULE, SAID HEATING TAKING PLACE AT A TEMPERATURE IN THE RANGE OF300* TO 500* F. FOR A TIME SUFFICIENTLY TO FORM SAID METAL SALT AND TOEVAPORATE SAID ALCOHOL.